Thermal detectors using graphene and oxides of graphene and methods of making the same

ABSTRACT

Radiation detecting and sensing systems using graphene and methods of making the same are provided; including a substrate, a single or multiple layers of graphene nanoribbons, first and second conducting interconnects each in electrical communication with the graphene layers. Graphene layers are tuned to increase the temperature coefficient of resistance, increasing sensitivity to IR radiation. Absorption over a wide wavelength range (200 nm to 1 mm) is possible based on the three alternative devices structures described within. Devices can variously include (a) a microbolometer based graphene film where the TCR of the layer is enhanced with selected functionalization molecules, (b) graphene layers with a source and drain metal interconnect and a deposited metal of SiO2 gate which modulates the current flow across the phototransistor detector, and/or (c) tuned graphene layers layered on top of each other where a p-type layer and a n-type layer is created using a combination of oxidation and doping.

RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/949,776, filed Nov. 23, 2015, entitled THERMAL DETECTORS USINGGRAPHENE AND OXIDES OF GRAPHENE AND METHODS OF MAKING THE SAME, whichapplication is a continuation of U.S. patent application Ser. No.13/870,959, filed Apr. 25, 2013, entitled THERMAL DETECTORS USINGGRAPHENE AND OXIDES OF GRAPHENE AND METHODS OF MAKING THE SAME, now U.S.Pat. No. 9,196,766, issued Nov. 24, 2015, which application claims thebenefit of U.S. Provisional Application Ser. No. 61/638,243, filed Apr.25, 2012, entitled THERMAL DETECTORS USING GRAPHENE AND OXIDES OFGRAPHENE AND METHODS OF MAKING THE SAME, the entire disclosures of eachof which applications is herein incorporated by reference.

FIELD OF THE INVENTION

The present application relates generally to bundled nanotube fabricsand methods of making graphene for use in Ultraviolet (UV), Infrared(IR) and Terahertz radiation detecting and sensing systems.

BACKGROUND OF THE INVENTION

Photodetectors are an integral part of optical circuits and components(for example emitters, modulators, repeaters, waveguides or fibers,reflectors, resonators, detectors, IR Focal plane arrays, UVmicrochannel arrays and THZ diode detectors etc.) and are used for thesensing of electromagnetic radiation. There are several approaches tothese devices. Photoconducting materials, typically semiconductors, haveelectrical properties that vary when exposed to electromagneticradiation (i.e. light). One type of photoconductivity arises from thegeneration of mobile carriers (electrons or holes) during absorption ofphotons. For semiconducting materials, the absorption of a specificwavelength of light, hence photon energy, is directly proportional tothe band gap of the material (E_(g)=hn=hc/l, where E_(g) is thematerials band gap, h is Plank's constant (4.136×10⁻¹⁵ eVs), c is thespeed of light in a vacuum (2.998×10¹⁰ cm/s) and 1 is the wavelength ofthe radiation). If the band gap energy is measured in eV (electronVolts) and the wavelength in micrometers, the above equation reduces toE_(g)=1.24/l. A photodiode (i.e. p-n diode, p-i-n photodiode, avalanchephotodiode, etc.) is the most commonly employed type of photoconductor.

Light detection is ideally suited for direct band gap semiconductorssuch as Ge and GaAs. However, indirect band gap semiconductors (where anadditional phonon energy is needed to excite an electron from thevalence band to the conduction band), such as Silicon, are also used asphotodetectors. A widely known type of photodetectors is the solar cell,which uses a simple p-n diode or Schottky barrier to detect impingingphotons. Besides silicon, most photodetectors disadvantageously do notintegrate with existing microelectronics technology, usually detect onlya specific wavelength (i.e. 1.1 mm for Si, 0.87 mm for GaAs, 0.414 mmfor a-SiC and 1.89 mm for Ge), and require multiple detectors to detecta broad band of wavelengths (hence photon energy).

Besides photodiodes, there are other types of photodetectors that do notrely on the generation of current through the excitation of electrons(or holes). One type of detector is the bolometer. Bolometers operate byabsorbing radiation, which in turn raises the temperature of thematerial and hence alters the resistance of the material. For usefulbackground information on bolometers and semiconductor devices, refer toKwok K. NG, “Complete Guide to Semiconductor Devices,” IEEE Press, JohnWiley & Sons, 2002, pages 532-533. Bolometers can be constructed frommetallic, metallic-oxides or semiconducting materials such as vanadiumoxide and amorphous silicon. Since bolometers detect a broad range ofradiation above a few microns, bolometers are typically thermallystabilized to reduce the possibility of detection of blackbody radiationthat is emitted from the detector material, which leads to a highbackground noise. Unlike other detector technologies, IR microbolometerdetectors and arrays advantageously do not require cooling to cryogenictemperatures unlike the other detector technologies discussed.

Graphene by the use of oxidation processing can induce a band gap ingraphene layers. Since graphene can also generate heat and phonons byseveral processes (injection of electrons, impinging with radiation,etc.), graphene is also ideally suited as an IR detector. For graphene,which has a zero electron volt bandgap, high mobilities (approximately100000 cm2/Vs) and carrier saturation velocities on the order ofapproximately 5×10E7 cm/s, these nanoribbons can serve as eitherphotodetectors or by modulation of the temperature coefficient ofresistance of the graphene layer(s), a microbolometer type of detector.

An existing prior art micro bolometer utilizes vanadium oxide as theelement which changes impedance for incoming IR radiation. Typically 2%per degree C. is the highest thermal coefficient of resistanceachievable. This performance is limited by 1/f noise and the basicphysical properties of the vanadium oxide film. The VOx based microbolometer is fabricated on top of the CMOS readout circuit, whichprovides a cost benefit.

Accordingly, it is desirable to provide graphene based UI, IR and THZradiation and light detecting systems to enhance overall sensitivity ofthe system.

SUMMARY OF THE INVENTION

The present invention overcomes the disadvantages of the prior art byproviding a light detector that includes a single graphene layer (ormultiple layered) article in electrical communication with a first and asecond contact; and a detection circuit in electrical communication withthe first and second contacts. The detection circuit provides electricaloutputs for sufficient light detection from the nanotube article in theproximity of the predefined region by use of preamplification.

In accordance with an illustrative embodiment, the predefined regionwhere graphene layer(s) are situated on a cantilever beam that providesthermal isolation from the surrounding environment.

In accordance with an illustrative embodiment, graphene is deposited andis exposed to an oxidation environment resulting in the creation of abandgap in the graphene layer. With the introduction of n or p dopants,a n-on-p or p-on-n photodiode is fabricated.

In accordance with an illustrative embodiment, the predefined region isbetween two electrical contacts. These electrical contacts provideelectrical communication and also are designed for maximum thermalisolation. Additionally, in order to create low electrical resistancegraphene to interconnect connection, the use of Palladium or platinum isdesirable to enhance pi bond connects in the graphene phase and themetal interconnects.

In accordance with an illustrative embodiment, the graphene baseddetector invention light detection arrays can be integrated withsemiconductor circuits including CMOS circuits which provide pixel arrayx-y controls, pre-amplification of the modulated resistance signal fromthe IR detector and the conversion of the analog signal to digital.

In accordance with an illustrative embodiment, the graphene nanoribbonfilm(s) increase the temperature coefficient of resistance from existingprior art of approximately 0.025% per degree Centigrade to in excess ofapproximately 0.04% per degree centigrade.

In accordance with an illustrative embodiment, a graphene basedmicrobolometer detects light by resistance changes in the fabric due toheating.

In accordance with an illustrative embodiment, the IR detector no longersuffers from the Nyquist frequency limitation. This is due to the factthat the Nyquist frequency limitation is due to the presence of 1/f orflicker noise. Graphene nanoribbons exhibit non measurable noise sourcesof these types. Within optical systems with f1, the elimination ofNyquist limited behavior is a vast improvement to IR detection systemsperformance.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention description below refers to the accompanying drawings, ofwhich:

FIG. 1 is a schematic diagram of a microbolometer detecting elementaccording to an illustrative embodiment employing a graphene sensingelement fabricated on a generic CMOS wafer process;

FIG. 2A is a schematic diagram of the resulting structure after a firststep is performed in fabrication of a graphene based thermal detector,in which a film is deposited on a substrate and standardphotolithography creates a hole over the tungsten (W) plugs, accordingto the illustrative embodiment;

FIG. 2B is a schematic diagram of the resulting structure after anotherstep is performed in the fabrication of the thermal detector, in which athin film of Cu is deposited, according to the illustrative embodiment;

FIG. 2C is a schematic diagram of the resulting structure after anotherstep is performed in the fabrication of the thermal detector, in which alayer of amorphous silicon is deposited, according to the illustrativeembodiment;

FIG. 2D is a schematic diagram of the resulting structure after anotherstep is performed in the fabrication of the thermal detector, in whichthe layer of amorphous silicon is planarized using chemical-mechanicalpolishing, according to the illustrative embodiment;

FIG. 2E is a schematic diagram of the resulting structure after anotherstep is performed in the fabrication of the thermal detector, in whichcontact holes are provided through the amorphous silicon and siliconoxide layers, thereby clearing the material down to the underlyingtungsten (W) plus, according to the illustrative embodiment;

FIG. 2F is a schematic diagram of the resulting structure after anotherstep is performed in the fabrication of the IR detector, in whichstandard CMOS interconnect metallurgy is deposited, according to theillustrative embodiment;

FIG. 2G is a schematic diagram of the resulting structure after anotherstep is performed in the fabrication of the IR detector, in which agraphene layer is deposited, according to the illustrative embodiment;

FIG. 2H is a schematic diagram of the resulting IR detector after thefinal step is performed in the fabrication of the IR detector, in whichthe graphene layer is masked off to create the image detector designdesired and the amorphous silicon in the cavity is etched, according tothe illustrative embodiment;

FIG. 3 is a perspective view of the fully assembled graphene basedmicrobolometer using a suspended graphene detecting element, inaccordance with an illustrative embodiment;

FIG. 4 is a top view of a matrix of graphene based microbolometers orphoto field effect transistor arrays comprising a focal plane array, inaccordance with the illustrative embodiments;

FIG. 5 is a schematic diagram of the CMOS readout circuit for thegraphene detector elements, in accordance with the illustrativeembodiments;

FIG. 6 is a graphical diagram of the measured film resistance of agraphene layer versus temperature, according to the illustrativeembodiment;

FIG. 7A is a schematic diagram of a photo-field effect transistor devicestructure incorporating a graphene layer or multilayer, in accordancewith the illustrative embodiments; and

FIG. 7B is a band gap diagram of the structure of FIG. 7A, according tothe illustrative embodiments.

DETAILED DESCRIPTION

Devices including graphene single layers or multilayers suspended overgaps (for example, gaps of approximately 50-250 nm) can be employed asInfrared (IR) radiation detectors. In addition, the application ofgraphene single layer or multilayers on a thermally isolated cantileverbeam can be employed as an IR radiation detector.

Graphene based detectors have several important and unique features thatare not available with existing technologies. First, arrays of thesenanotube light detectors can be formed using patterning technology atminimum dimensions of the lithography node used or dictated by thedemands of the optical imaging system. It is possible to create 25, 17,or 8 micron square or less detectors limited only by photolithographytechniques.

Illustrative embodiments of the invention allow integration at a levelof one light detector per ten or less transistors at the minimumdimension of a given lithography node or the integration of large arraysthat are addressed by CMOS pre-amplification or readout and logiccircuits. Previously only discrete components, such as silicon p-ndiodes, could be used as light detectors for optoelectronic circuits.Other types of detectors require complex and difficult fabricationtechniques such as flip-chip processes to integrate with siliconsemiconductor technology. Because CNT light sensors can be integrated toform VLSI arrays, which allows for optical interconnects having onelight detector per transistor (or waveguide, depending on function), thefabrication of ultra-dense optical circuits is possible.

According to illustrative embodiments, light detecting elements have asuspended region of nanofabric overlying a substrate material. FIG. 1shows a schematic diagram of an IR detector having a graphene basedfabric sensing element fabricated on a generic CMOS wafer. The IRdetector incorporates a graphene based fabric sensing element forperforming the infrared detection. The IR detector 100 includes aconventional P-N junction substrate 101, which is part of the overallCMOS logic 110. The substrate 101 can comprise silicon using a Bridgmanfloat zone technique. There is a film 120 deposited on the substrate 101as well as the graphene nanoribbon IR sensors 130, for performing the IRdetection. The film 120 can comprise a silicon oxide layer based uponthe absorption frequency for the type of device. The IR detector 101 isfabricated in accordance with the procedures outlined in FIGS. 2Athrough 2I.

Light detectors can be constructed using suspended or non-suspendednanotube-based fabrics in combination with appropriate substrates.Fabrication techniques to develop such horizontally- andvertically-disposed fabrics and devices composed of nanotube fabricswhich comprise redundant conducting nanotubes may be created via CVD, orby room temperature operations as described herein. For usefulbackground material on fabrication of carbon nanotubes, refer to U.S.Pat. No. 6,706,402, and published PCT Application No. WO 01/03208, whichare expressly incorporated by reference herein. Because creation ofsuspended graphene-based detector elements is like fabrication ofsuspended nanotube-based memory elements described in the incorporatedU.S. Pat. No. 6,706,402 and WO 01/03208, reference can be made to thesematerials for background information on the fabrication of suspendedgraphene-based detector elements. Such detectors can be part of a schemeinvolving signal transmission or use in a display.

The substrate material 101 can be an insulator such as one describedhereinabove or can be a semiconductor (such as, but not limited to, Si(single crystal, polycrystalline and amorphous), Ge, SiGe, SiC, Diamond,GaN, GaAs, GaP, AlGaAs, InP, GaP, CdTe, AlN, InAs, Al_(x)In_(1-x)P, andother III-V and II-VI semiconductors) or a conductor (such as, but notlimited to, Al, Cu, W, Al(<1% Cu), Co, Ti, Ta, W, Ni, Mo, Pd, Pt, TiW,Ru, CoSi_(x), WSi₂, TiSi_(x), TaN, TiN, TiAlN, RuN, RuO, PtSi, Pd₂Si,MoSi₂, NiSi_(x)). The substrate material systems can be chosen forcircuitry technologies and light absorption considerations, the graphenefabric and associated microbolometer structure processing are compatiblewith all of these materials. The suspended region (see region 272 ofFIG. 2H) defines the electromagnetic sensing region of the detectingelement 100.

The layers are composed of several layers of overlapping graphene layersto create a multilayered film of greater than approximately 10 nm. Thegraphene layer(s) can be grown or deposited on a surface, as describedhereinabove, to form a contiguous film of a given density. Typically,the lower dimension sizes of the nanotube film are a consequence oflithographic technology limitations and not any limitations of theillustrative embodiments herein. After patterning, the graphene layerscan be further integrated with metal interconnects and dielectricpassivation layers to create a circuit element. The light detection fromthe detecting element 130 is controlled by driving circuitry. Refer toFIG. 5 for a diagram of exemplary driving circuitry 510, 520, 521 and530.

Light detectors can be constructed using suspended or non-suspendedgraphene-based fabrics in combination with appropriate substrates.Fabrication techniques to develop such horizontally- andvertically-disposed fabrics and devices composed of nanotube fabricswhich comprise redundant conducting graphene can be created via CVD, orby room temperature operations as described herein and others known inthe art. Refer, for example, to U.S. Pat. Nos. 6,574,130, 6,643,165,6,706,402, 6,784,028, 6,835,591, 6,911,682, 6,919,592, and 6,924,538,for useful background information on fabrication of graphene-basedfabrics.

Light can be impinged on the open area of these bundled carbon nanotubefabrics to cause the generation of heat in the fabric, such as abolometer. Or in the case of the phototransistor based photodetectorsthe absorbed light carriers

Suspended graphene layers are ideal structures for monolayered fabrics,which have a high porosity. Since the substrate may influence thedetection of radiation, the suspended region should diminish anydisadvantageous substrate thermal isolation effects.

Reference is now made to FIGS. 2A-2H, showing the various stages of thefabrication procedure for an IR detector incorporating graphene layers.Standard CMOS microelectronics processing techniques, graphenenanoribbon process flow or the CVD (chemical vapor deposition) processcan be employed to fabricate the detector in accordance with theillustrative embodiments herein. As shown in FIG. 2A, using standardCMOS microelectronics processing techniques, a deposited silicon oxidefilm 201 is deposited on the substrate 202. A standard photolithographymethod, known in the art, is used to create a hole 205 over the tungsten(W) plugs. The Tungsten plugs 203 serve as interconnects to theunderlying CMOS pre-amplification circuitry 204. Refer to FIG. 5 for adiagram of an exemplary CMOS circuitry. The next step, as shown in FIG.2B, is to use electron beam evaporation or direct current sputtering todeposit a thin film of Copper (Cu) 211 which serves as an IR photonreflector.

As shown in FIG. 2C, in the next step of the fabrication process a layerof amorphous silicon 220 is deposited and planarized usingchemical-mechanical polishing to result in the amorphous silicon 230 ofFIG. 2D. The next step is use standard photolithography techniques usinga photoresist stencil and reactive ion etching to etch contacts holes240 through the amorphous silicon and silicon oxide layers clearing thematerial down to the underlying tungsten plugs which serve asinterconnects to the underlying CMOS circuitry, as shown in FIG. 2E. Thenext step is to use direct current sputtering to deposit standard CMOSinterconnect metallurgy, aluminum-copper thin films 250. Standardphotolithographic/dry etch techniques are used to delineate theinterconnect structures, as shown in FIG. 2F. The next step, as shown inFIG. 2G, is to deposit graphene layer(s) 260. The final steps are tomask off the graphene fabric and employ standard photolithographicmethods to create the image the detector design required. Finally usingXeFl2 (Xenon Difluoride) etching, or other techniques known in the art,the amorphous silicon in the cavity is etched and a gap or cavity 272 iscreated, which results in the fully fabricated device as shown in FIG.2H having a suspended region of graphene-based fabric 270 overlying thegap 272. Also refer to FIG. 3 for a perspective view of the fullyfabricated device.

One indicator for process optimization is to use CNT based field effecttransistors (for example as shown in FIG. 7A) and measure the ratio ofthe current on over the current off. After the optimized space isdetermined then the process is further optimized by examining thegraphene sheets with Transmission Electron Microscope for defects,electronic mobility and degree of CNT rupture.

Reference is now made to FIG. 3, showing a perspective view of a fullyassembled graphene based microbolometer, according to an illustrativeembodiment. A graphene based microbolometer structure 300 is shown,having readout locations 310. The structure 300 includes a graphenenanoribbon fabric 312 suspended above the substrate 313, in accordancewith the techniques described herein and readily apparent to thosehaving ordinary skill. The thermally isolated cantilever structure 314is also shown, as well as the connection to tungsten (W) plugs 316. Anarray of graphene nanoribbon based microbolometers is shown in the topview of FIG. 4, in accordance with the illustrative embodiments. Thearray 400 of microbolometers includes a plurality of microbolometers401, 402, 403, 404, 405, 406, 407, 408, 409, 410, 411, 412, 413, and414.

FIG. 5 is a schematic diagram of an exemplary CMOS readout circuit forthe graphene nanoribbon IR detector in accordance with the illustrativeembodiments. As shown in the diagram 500, there is a common half circuit510 operatively connected to a unit cell circuit 520 which includes theIR detector 521. A dynamic discharging output stage circuit 530 isoperatively connected to the unit cell circuit 520 to define the overallCMOS readout circuit 500.

FIG. 6 is a graphical diagram of the measured film resistance of thegraphene layer versus the temperature, according to the illustrativeembodiments. As described hereinabove, the electrical resistance of themicrobolometers changes as the temperature rises due to the absorptionof electromagnetic radiation in the fabric. This is illustrated in thegraphical diagram 610 of FIG. 6. As shown, during both the first pass621 and the second pass 622, as the temperature increases, theresistance of the microbolometer changes. Accordingly, this allows thestructure to be employed as an IR detector in accordance with theillustrative embodiments.

Reference is now made to FIG. 7A showing a schematic diagram of aphoto-field effect transistor device structure incorporating a graphenelayer or multilayer, according to an illustrative embodiment. As shown,the fully assembled IR detector is operatively connected to source andground where appropriate to provide a photo-field effect transistor. Asource 701 and drain contact 702 are deposited and etched onto a siliconoxide layer 703 that is deposited on a substrate 704, such as silicon,GaAs, or other compound semiconductors. Graphene layers 705 arefabricated and deposited on the silicon oxide layer 703. The next stepis to expose the graphene layers to an oxidation environment atsufficient temperature. Each layer is then exposed to a dopant eithern-type of p-type and then the next graphene layer is exposed to theopposite dopant type creating a n-on-p or p-on-n structure. A CMOScompatible thin film metal 706 is then deposited, such as palladium orplatinum, upon which the source and drain contacts 701, 702 arefabricated.

A metal or oxide gate electrode 707 is fabricated on top of the graphenelayer or layers. The gate electrode 707 can comprise a deposited metalof SiO2, which modulates the current flow across the phototransistordetector. In some embodiments, it may be necessary to fabricate a space708 between the top of the graphene and the bottom of the metal orsilicon oxide gate electrode.

FIG. 7B shows a band gap diagram of the photo-field effect transistor ofFIG. 7A. As shown, with the initiation of photon illumination, electronsmove either towards the Vd level or into the conduction band. Holes movetoward the Vg level, thereby creating a depletion region in the p-njunction.

The various illustrative embodiments afford efficient thermal detectorsby employing graphene layers. Oxidation of the graphene results insemiconducting behavior and, with the addition of a n-type or p-typedopant, results in either n-on-p or p-on-n diode devices with very highmobility. This results in high sensitivity and fast detector responseoperation. The resulting devices can be optimized for detection of UVand Terahertz radiation, in accordance with the illustrativeembodiments.

The teachings herein can be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresent embodiments are therefore to be considered illustrative and notrestrictive, the scope of the invention being indicated by the appendedclaims rather than by the foregoing description.

The foregoing has been a detailed description of illustrativeembodiments of the invention. Various modifications and additions can bemade without departing from the spirit and scope of this invention. Eachof the various embodiments described above may be combined with otherdescribed embodiments in order to provide multiple features.Furthermore, while the foregoing describes a number of separateembodiments of the apparatus and method of the present invention, whathas been described herein is merely illustrative of the application ofthe principles of the present invention. For example, the illustrativeembodiments can include additional layers to perform further functionsor enhance existing, described functions. Likewise, the electricalconnectivity of the cell structure with other cells in an array and/oran external conduit is expressly contemplated and highly variable withinordinary skill. Additionally, it is expressly contemplated thatsingle-wall nanotubes, multi-wall nanotubes, and any combinationthereof, can be employed. More generally, while some ranges of layerthickness and illustrative materials are described herein, these rangesare highly variable. It is expressly contemplated that additionallayers, layers having differing thicknesses and/or material choices canbe provided to achieve the functional advantages described herein. Inaddition, directional and locational terms such as “top,” “bottom,”“center,” “front,” “back,” “on,” “under,” “above,” and “below” should betaken as relative conventions only, and are not absolute. Furthermore,it is expressly contemplated that various semiconductor and thin filmfabrication techniques can be employed to form the structures describedherein. Accordingly, this description is meant to be taken only by wayof example, and not to otherwise limit the scope of this invention.

What is claimed is:
 1. A graphene based detector comprising: a thin filmof graphene suspended between electrical contacts; first and secondconductive terminals in electrical communication with the thin film ofgraphene; wherein the thin film of graphene is tuned such that exposureof radiation induces a change in impedance between the first and secondconductive terminals which is sensed by CMOS readout circuitry; whereinthe thin film of graphene nanoribbon is tuned to increase thesensitivity of the detector by exposing the graphene nanoribbon to anoxidation environment at a predetermined temperature, which therebyincreases the thermal coefficient of resistance (TCR) to excess of 4percent per degree centigrade and up to 6 percent per degree centigrade,thereby resulting in a Noise Equivalent Delta Temperature (NEDT) of lessthan 10 mK.
 2. The graphene based detector of claim 1 further comprisingsensing circuitry for detecting changes in input impedance using theCMOS readout circuitry.
 3. The graphene based detector of claim 1wherein the thin film of graphene is tuned to be sensitive to Infrared(IR) radiation in the micron band of 1 to 12 microns and the radiationthat induces the change in impedance comprises IR radiation.
 4. Thegraphene based detector of claim 1 wherein the thin film of graphene istuned to be responsive to a selected functionalization molecularspecies, to achieve responsivity to Ultraviolet (UV) or Terahertz (THZ)radiation.
 5. The graphene based detector of claim 1 wherein the thinfilm of graphene is deposited on a substrate having an insulating layercomprised of dielectric material with a cantilever beam composed ofsilicon nitride, which is suspended over a channel, thereby providingthermal isolation from surrounding environments.
 6. The graphene baseddetector of claim 1 wherein the thin film of graphene is deposited onvanadium oxide and amorphous silicon to assist in the improvement ofphoton absorption.
 7. The graphene based detector of claim 1 wherein thefirst and second conductive terminals comprise one of: palladium andplatinum, thereby enhancing the pi bonding to the thin film of grapheneand reducing contact resistance.
 8. The graphene based detector of claim1 wherein the thin film of graphene is optimized for wavelengthabsorption by use of functionalization molecules or nanoparticles tunedto a predetermined wavelength.
 9. A graphene based detector comprising:a thin film of graphene suspended between electrical contacts; first andsecond conductive terminals in electrical communication with the thinfilm of graphene; wherein the thin film of graphene is tuned such thatexposure of radiation induces a change in impedance between the firstand second conductive terminals; wherein the thin film of graphenenanoribbon is tuned to increase the sensitivity of the detector byexposing the graphene nanoribbon to an oxidation environment at apredetermined temperature, which thereby increases the thermalcoefficient of resistance (TCR) to excess of 4 percent per degreecentigrade and up to 6 percent per degree centigrade, thereby resultingin a Noise Equivalent Delta Temperature (NEDT) of less than 10 mK. 10.The graphene based detector of claim 9 further comprising sensingcircuitry for detecting changes in input impedance using the CMOSreadout circuitry.
 11. The graphene based detector of claim 9 whereinthe thin film of graphene is tuned to be sensitive to Infrared (IR)radiation in the micron band of 1 to 12 microns and the radiation thatinduces the change in impedance comprises IR radiation.
 12. The graphenebased detector of claim 9 wherein the thin film of graphene is tuned tobe responsive to a selected functionalization molecular species, toachieve responsivity to Ultraviolet (UV) or Terahertz (THZ) radiation.13. The graphene based detector of claim 9 wherein the thin film ofgraphene is deposited on a substrate having an insulating layercomprised of dielectric material with a cantilever beam composed ofsilicon nitride, which is suspended over a channel, thereby providingthermal isolation from surrounding environments.
 14. The graphene baseddetector of claim 9 wherein the thin film of graphene is deposited onvanadium oxide and amorphous silicon to assist in the improvement ofphoton absorption.
 15. The graphene based detector of claim 9 whereinthe first and second conductive terminals comprise one of: palladium andplatinum, thereby enhancing the pi bonding to the thin film of grapheneand reducing contact resistance.
 16. The graphene based detector ofclaim 9 wherein the thin film of graphene is optimized for wavelengthabsorption by use of functionalization molecules or nanoparticles tunedto a predetermined wavelength.